1. Field of the Invention
This invention relates to a power transmission device in a transfer press machine for transmitting the driving force of the press body side to the feeder device side, and more particularly relates to the coupling control of the power transmission device.
2. Description of the Prior Art
In a transfer press, there is provided a transfer feeder which carries workpieces to each working station. The transfer feeder usually obtains the driving force from the press body side via a power transmission device connecting between the press body and the transfer feeder, and, by this driving force, conveys workpiece by two-dimensionally or three-dimensionally moving transfer bars synchronizing with the movement of slides in the press body side.
In the above-described power transmission device, other than a mechanism which performs the synchronized operation of the press body and the transfer feeder by obtaining the driving force from the press body, there is provided a motor for independent operation so as to be able to independently operate only the transfer feeder.
Now, in a press machine provided with such a power transmission device, when a mold is exchanged, the coupling of the power transmission device is once released, and is coupled again after the completion of the exchange of the mold. Further, in this kind of device, in order to prevent mechanical damage due to the overload applied to the transfer feeder, the coupling of the power transmission device is automatically released when the overload is generated. The recoupling of the power transmission device becomes also necessary in such situation.
On the occasion of such a recoupling, when the locating between the shaft angle of the feeder side and the crank angle of the press is deviated, it becomes impossible to synchronize the transfer feeder with the press body. Hence, in the conventional device, the operator performs the following series of coupling operations.
(1) By operating a forward rotation/reverse rotation switch of the motor for the independent operation of the feeder, the operator adjusts the angle of the feeder-side shaft to the angle of the press body-side shaft with watching a display unit.
(2) When the above-described angles coincide with each other, the operator closes a coupling switch to recouple the power transmission device.
Thus, in the conventional device, in order to couple the power transmission device, it is necessary to perform troublesome operations relative to the adjustment of the angles of shafts or the like. Moreover, since the adjustment of angles is difficult, there is a problem in that only skilled operators who are aquainted with the movement of the machine can perform sure coupling.
The present invention takes into consideration such circumstances. It is an object of the present invention to provide a power transmission device of a press machine which can automatically couple a power transmission device with only excellent locating accuracy only by performing only simple operations.